Priority is claimed to Patent Application Numbers 2001-26417 filed in Rep. of Korea on May 15, 2001 and 2002-2217 filed in Rep. of Korea on Apr. 23, 2002, both herein incorporated by reference.
1. Field of the Invention
The present invention relates to an evaporator of a cooling apparatus, and more particularly, to an evaporator of a capillary pumped loop (CPL) cooling apparatus having a fine wick structure.
2. Description of the Related Art
Although power required to drive a semiconductor device comprising chips is very small, if the number of chips in the semiconductor device, that is, if the integration of chips, is high, heating values for areas increase, and the surface temperatures of chips accordingly increase.
If the surface temperature of chips increases, their reliability and life span are reduced.
Accordingly, various methods for cooling chips have been suggested. One of the methods uses a capillary pumped loop (CPL) in which the surface tension of coolant in a fine structure is used as part of a driving force for circulating coolant.
The CPL is comprised of an evaporator for contacting a heating body and absorbing heat from the heating body, a condenser for condensing vapor, and a liquid tube and a vapor tube connected between the evaporator and the condenser.
The temperature and pressure of the vapor generated in the evaporator are higher than the vapor of the condenser. Thus, the vapor generated in the evaporator naturally flows into the condenser. In the condenser, the vapor is condensed to become liquid. The liquid flows into the evaporator by a capillary action generated in the liquid pipe and the evaporator having a fine wick structure and is used as coolant cooling the heating body.
The cooling performance of the CPL depends on the structure and connection of elements. In particular, the structure of the evaporator for absorbing heat from the heating body and pumping liquid condensed by the condenser plays a more important role in the cooling performance of the CPL.
The design of a flowing-out structure for transporting vapor generated by absorbing heat from the heating body, from the evaporator into the condenser, and a fine structure for flowing liquid condensed by the condenser into the evaporator without a dry-out phenomenon (a phenomenon that the flow of liquid is cut off on the surface of the evaporator, and thus the surface of the evaporator dries out) are the most important considerations when designing an evaporator.
In a case where the flowing-out of vapor generated in the evaporator and flowing-in of liquid from the condenser into the evaporator are performed in balance, an evaporator of a CPL cooling apparatus capable of stable and high performance can be realized. However, a conventional evaporator of a CPL cooling apparatus does not meet this requirement.
To solve the above problem, it is an object of the present invention to provide an evaporator of a capillary pumped loop (CPL) cooling apparatus which is capable of balancing the flowing-out of evaporated vapor with the supply of coolant, performing stably and improving cooling efficiency.
Accordingly, to achieve the above object, according to one aspect of the present invention, there is provided an evaporator of a capillary pumped loop (CPL) cooling apparatus comprising a condenser, an evaporator for being supplied coolant from the condenser and cooling a heating body according to variation in a phase of the coolant. The evaporator having a flat board shape, of a CPL cooling apparatus includes a coolant storing part for storing in-flowing coolant from the condenser and collecting a uncondensed gas contained in the in-flowing coolant in an upper space, a cooling part for cooling the heating body through vaporization of the coolant, and superstructure and substructure combined with each other, for defining a channel region in which the coolant flows from the coolant storing part to the cooling part by a capillary action.
The substructure includes a first substructure used as a substrate, and a second substructure forming a coolant inlet formed along a border of the first substructure and connected to a coolant outlet of the condenser between the substructure and the superstructure, and a vapor outlet connected to a vapor inlet of the condenser.
The channel region is formed between the coolant storing part and the cooling part, and part of the channel region is extended between the cooling part and the second substructure.
It is also preferable that the bottoms of the coolant storing part, the channel region, and the cooling part are comprised of at least one pattern region.
It is also preferable that the cooling part includes two pattern regions. That is, predetermined patterns (hereinafter, is referred to as heated portion pattern region) are included in a region corresponding to a heated portion. Further, one other pattern region for completely surrounding the heated portion pattern region is included between the channel region and the heated portion pattern region. Further, one other pattern region includes a region in which at least two different patterns are formed.
It is also preferable that a plurality of patterns are formed in at least one region of the coolant storing part, the channel region, or the bottom of the cooling part such that the coolant flowing from the condenser or other adjacent pattern regions flows into the cooling part or the center of the cooling part isotropically or anisotropically. In this case, each of the plurality of patterns allowing the coolant to flows anisotropically has a predetermined height and a predetermined geometrical shape in which the flat shape of each of the plurality of patterns has a predetermined length in a direction of the flow of the coolant, and the height of the plurality of patterns is higher or lower than the height of patterns formed in the adjacent pattern regions.
A plurality of patterns are distributed in one pattern region of the pattern regions forming the cooling part such that the coolant flowing from the adjacent pattern region flows into the center of the cooling part, and simultaneously isotropically flows into the entire own pattern region.
A plurality of patterns are distributed in the center of the cooling part such that the coolant flowing from the adjacent pattern region uniformly and quickly flows into the entire own pattern region, and simultaneously transfers heat generated from the heating body in a vertical direction. In this case, each of the plurality patterns has a predetermined height and a predetermined geometrical shape, and the thicknesses of the plurality of patterns become smaller and their heights become higher from the center of the cooling part.
In order to achieve the above object, according to another aspect of the present invention, the substructure includes a first segment comprising the coolant storing part together with the superstructure and forming a coolant inlet connected to the coolant outlet of the condenser, second segment being opposite to a side defining the channel region of the superstructure and whose one side adheres closely to the first segment so that the coolant is not leaked, and a third segment comprising the cooling part together with the superstructure, forming a vapor outlet connected to the vapor inlet of the condenser and adhering closely to the other side of the second segment so that the coolant is not leaked.
It is preferable that step exists between the first and second segments and/or between the second and third segments.
It is also preferable that a pumping means for pumping the coolant filling the channel region and flowing into the coolant storing part to the cooling part is included between the second segment and the side defining the channel region of the superstructure. The pumping means is formed of a porous material. The pumping means is formed of a porous material and patterns formed in part of the second segment, and the patterns are formed so that the capillary action is generated in the coolant flowing into the coolant storing part or the in-flowing coolant through the porous material.
It is also preferable that part of the channel region is extended into the cooling part and a vertical portion of the third segment. Another part of the channel region is extended into the coolant storing part and a vertical portion of the first segment.
According to the present invention, a coolant storing part for separately storing a uncondensed gas and liquid is included in the evaporator of a CPL cooling apparatus, and thus, the coolant can be stably supplied to the cooling part, and the present invention can prevent the uncondensed gas from flowing into the condenser and accumulating on the condenser, thereby uniformly and continuously supplying the coolant removed by evaporation in the cooling part from the coolant storing part to the cooling part and improving cooling efficiency.